The invention concerns a process to control vehicle acceleration for a motor vehicle having a continuously variable automatic transmission.
According to the belt-drive principle, a continuously variable automatic transmission (CVT transmission) is usually comprised, of a starting unit, a forward/reverse drive unit, an intermediate shaft, a differential, hydraulic and electronic control devices and a variator, among others. The variator usually comprises a primary and a secondary pulley, both pulleys formed of beveled pulleys disposed in pairs, and is provided with a torque-transmitting, belt-drive element which rotates between both beveled pulley pairs. In a transmission of that kind the actual ratio is defined by the running radius of the belt-drive element which, in turn, is a function of the axial position of the beveled pulleys.
Consequently, subject to construction, during a change of ratio the beveled pulley pairs of the primary and secondary pulleys of the variator are alternately and complementally to each other, pushed apart and pushed together, which produces a change of the running radius of the belt-drive element on the beveled pulleys and thus a change of ratio between primary and secondary sides.
According to the prior art and depending on the existing design and under circumstances a downshift produces a deceleration of the vehicle while an upshift produces a corresponding acceleration, but the effects are not always desirable.
Based on the prior art, this invention is based on the problem of outlining a process for controlling acceleration of a vehicle having a continuously variable automatic transmission, to prevent an undesired deceleration or acceleration of the vehicle during the shifting operation, and make the acceleration curve adjustable per unit time.
In addition, the driver""s comfort must be increased and the drive train oscillations reduced.
It is, therefore, proposed to control vehicle acceleration by adjusting the ratio of the continuously variable automatic transmission by addition of a model-based control which uses a status estimating method to assess the output torque.
According to the invention, within the scope of the control, the tractional resistance torque is assessed by means of an interference level observation. A drive train pattern is used for this.
The tractional resistance torque is delivered as a variable pattern by interference level observation, whereby a very precise relationship is created and maintained between vehicle acceleration and ratio gradient.
Consequently, driving strategy possibilities result, defining the concept of spontaneity and, e.g. making downshifts applicable. By the proposed vehicle acceleration control, via ratio adjustment, it is possible to implement sporting, instantaneous downshifts and upshifts.